1. Field of the Invention (Technical Field)
The present invention relates to a nonmetallic input device, and an optical switch therefor, for transmitting reactions from a subject being studied or tested using magnetic imaging, including but not limited to functional magnetic resonance imaging (MRI), or for other uses that require the switching and/or transmission of a signal in a magnetic field.
2. Background Art
Note that the following discussion refers to a number publications and references. Discussion of such publications herein is given for more complete background of the scientific principles and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
There are a number of techniques used to image brain function in a subject individual whose reactions or responses are studied. One such technique, Functional Magnetic Resonance Imaging (fMRI) consists of using a Magnetic Resonance (MR) scanner to image a subject's brain while the subject is presented with a functional task or paradigm. The functional task may comprise auditory and/or visual stimuli. It may be necessary and/or desirable to have the subject respond and make decisions based on the stimuli that are presented to them. The experimenter receives and records subject responses, preferably using the stimulus presentation software used to present the auditory and visual stimuli. Another such technique, Magnetoencephalography (MEG), is another form of magnetic imaging similar to MRI in that they both are imaging tools that use high magnetic fields.
For such applications the subject is situated within the magnet room or magnetic field of the imaging device. Therefore, devices to collect responses from the subject must also be located within the magnetic field. Such input devices must therefore be completely nonmagnetic. It is preferable that the device is entirely nonmetallic as well. Metallic components act as antennas and thus introduce noise, which must be filtered out using, for example, radio frequency (RF) filters.
Therefore, it is preferable that nonmetallic switches, such as optical switches, are used in such input devices. All-plastic input devices which use optical switching via optical cables are manufactured by numerous companies and are known in the art. However these devices have a number of disadvantages. They have a touchpad or keypad configuration, which requires that the subject either hold the device in one hand and operate the switches with the other hand, or that the device rest on a surface and the subject's fingers rest on the switches. This is disadvantageous because for numerous magnetic imaging applications, the subject is not able to operate the device with both hands, or comfortably or stably rest his or her hand on a horizontal surface. Further, with these devices, it is easy for the subject's fingers to move from the switches, for example but not limited to sliding laterally off one or more switches. The subject must frequently reposition his or her fingers, thus interfering with the magnetic imaging data collected. Also, these prior art devices do not immobilize the subject's wrist. This permits wrist movement at any time during the experiment, resulting in motor cortex activation which may be confused with activation that is desired to be recorded. In addition, many such existing devices require electronics, such as an opto-electric converter, to be situated within the magnet room, thus inducing noise in the system and requiring costly filters. Finally, these devices typically use plastic membrane-type switches, which are prone to failure.
Thus there is a need for a nonmetallic input device and nonmetallic switch for use particularly in magnetic imaging applications, or any other application which requires manual switching or signaling in the presence of a magnetic field, which is comfortable, robust, and which prevents the movement of fingers from the switches corresponding to each finger.